Case Study: Microtunneling for a Large Diameter Watermain

Nathaniel Andres, P.Eng. R.V. Anderson Associates Limited

AGENDA

• Zone 3 Watermain – Project Overview

• Railway Crossing Details

• Typical Design Considerations

• Compliance and Regulatory Procedures

• Conclusions

ZONE 3 WATERMAIN – PROJECT OVERVIEW

• Scope: 4 km of trunk watermain (900mm diameter and 1200mm diameter CPP)

• Purpose: support population in approved growth areas and improve security of water supply in North Oakville and Milton

ZONE 3 WATERMAIN – PROJECT OVERVIEW

• Construction: largely open cut -- bridge over Bronte Creek -- microtunnel under railway

• Location: Dundas Street in Burlington / Oakville from Appleby Line to Bronte Road

Gravelly Sand

Sand

FillClayey Silt Till

Sandy Silt

Weathered Shale

RAILWAY CROSSING DETAILS

• Alternatives considered:

Pipe Ramming

• Challenge to keep liner on grade (auger head must be one pipe diameter behind liner face)

• Challenge to keep liner on grade

• Excessive vibration / noise

• Potential for surficial heave

Jack & Bore

RAILWAY CROSSING DETAILS

Microtunneling

• Ward & Burke Microtunneling Ltd.

• 1500Ø concrete casing / jacking pipe

• 900Ø watermain

• Entry Shaft: 7m diameter

• Exit Shaft: 5m diameter

RAILWAY CROSSING DETAILS

• Shaft Construction

• Caissons

• 2.5 metre high, poured-in-place concrete segments

• Tremie concrete in the base

• Dewatered after installation

Gravelly Sand

Sand

FillClayey Silt Till

Sandy Silt

Weathered Shale

7m

TYPICAL DESIGN CONSIDERATIONS

• Subsurface Conditions

• Groundwater

• Stiffness

• Consistency

• Gravel / Cobbles / Boulders

Cont’d

• Length of Drive

• Typical range for microtunneling is 50 – 500m

• Shorter = less cost competitiveness

• Longer = increased friction and jacking forces

Jacking

PipeWatermain

30mm Annular Space Filled with Grout

Zone 3 WM Cross Section

TYPICAL DESIGN CONSIDERATIONS

• Spatial Constraints

Entry Shaft and Control Unit

Pipe Storage

Separation System

COMPLIANCE AND REGULATORY PROCEDURES

• Railway Approvals

• Reviews by Rail Authority and their geotechnical consultant

• Settlement Monitoring Plan required

• Flagging is conducted by a Rail Authority representative

• Refer to Rail Authority guidelines

CONCLUSIONS

• Benefits Realized in Zone 3 Watermain Railway Crossing

• Minimal Dewatering

• Tolerance for mixed subsoils

• No delays / additional costs

• Minimal Settlement

• Timely completion

(~1 month)

QUESTIONS?

Nathaniel Andres, P.Eng. R.V. Anderson Associates Limited

nandres@rvanderson.com 416-497-8600 ext. 362